Spanishflower is correct, but DNA can be (is) copied in both directions. This happens because two replication forks move apart from one another, each copying one of the strands. Both replication forks are creating DNA in the 5' to 3' direction, but are copying different strands. So, replication with a single replication fork happens in only one direction, but two forks are common and result in the parent strand being copied in both directions at once.